1. Field of the Invention
The present invention relates in general to a method for producing beryllium chloride dietherate, and in particular, is directed to a low temperature method of producing beryllium chloride dietherate.
2. Description of the Related Art
Beryllium chloride is prepared by heating a mixture of beryllium oxide and carbon in chlorine at 600.degree.-800.degree. C. according to the following equation: ##STR1##
Alternative methods included the reaction of sulphur monochloride or phosgene with beryllium oxide, or the direct chlorination of beryllium carbide at 800.degree. C.
Beryllium chloride is not conveniently made by direct hydrochlorination of beryllium oxide as is illustrated in the following reaction: ##STR2##
The equilibrium of the above reaction lies to the left except at very high temperatures.
A problem in the synthesis of beryllium chloride is the ease with which the tetrahydrate (BeCl.sub.2 .cndot.4H.sub.2 O) undergoes hydrolysis during dehydration. Accordingly beryllium chloride is usually used under anhydrous conditions.
Numerous complexes of the type BeCl.sub.2 X.sub.2, where X represents a wide variety of organic ligands, have been prepared either by direct interaction or by addition of the ligand to an ethereal solution of beryllium chloride. These types of complexes include pyridine, acetone, nitriles, aldehydes, quinoline, aliphatic amines, piperidine, thiourea, and tetrahydrofuran. All of these complexes are decomposed by water and must be prepared under anhydrous conditions.
One of the more important of the beryllium chloride addition complexes is the dietherate, BeCl.sub.2 .cndot.2Et.sub.2 O. It is obtained by dissolving anhydrous beryllium chloride in dry ether which forms two liquid layers. The top layer is a solution of BeCl.sub.2 .cndot.2Et.sub.2 O in ether with the lower layer being a solution of ether in BeCl.sub.2 .cndot.2Et.sub.2 O. The compound is crystallized from the lower layer.
Ether solutions of beryllium chloride are used as the starting material in the production of beryllium alkyls or other beryllium-organic compounds as taught in U.S. Pat. No. 3,262,888 for example. These solutions are generated by the addition of BeCl.sub.2 to ether under anhydrous conditions. For example, U.S. Pat. No. 3,822,320 describes the synthesis of beryllium chloride monodiethyletherate.
Various approaches for the preparation of beryllium hydrides are disclosed in U.S. Pat. Nos. 3,865,928; 3,885,025; 3,917,809; 3,919,320; and 3,991,121.
Another reference of interest is U.S. Pat. No. 4,581,065 which discloses a process for metallothermic reduction of beryllium oxide, beryllium minerals and beryllium containing metal oxides.
A different approach in preparing beryllium chloride dietherate is described in U.S. Pat. No. 3,780,118 which discloses the use of a Soxhlet extractor. Beryllium metal chips are placed on top of a glass wool filter plug at one side and towards the top of the Soxhlet extractor. Reagent anhydrous diethyl ether is placed in the vessel below the Soxhlet extractor and hydrogen chloride is bubbled in through awash bottle containing concentrated sulfuric acid. While this process is suitable for laboratory scale preparation of beryllium chloride dietherate, it does not offer a solution for the commercial manufacture of large quantities of beryllium compounds. Furthermore, the Soxhlet method requires the beryllium metal to be suspended away from the desired product. It is known in the art that there is difficulty in getting this reaction to proceed or go to completion when the beryllium metal is in contact with the beryllium chloride etherate.
Another problem in the production of beryllium chloride is the extremely high toxicity of beryllium particularly when it is in the form of easily volatile compounds such as beryllium chloride or beryllium fluoride (BeF.sub.2).
Thus, there is a need for a low cost method for producing BeCl.sub.2 .cndot.2Et.sub.2 O). The product must be capable of being purified in a simple and straightforward manner. Also, the process must produce BeCl.sub.2 .cndot.2Et.sub.2 O at a lower cost than the prior art methods by using low temperature equipment. There is also a need for this method to improve the health and safety conditions of the workers who may be exposed to the formation of toxic beryllium vapors at high temperatures.